1. Field of the Invention
The invention relates to an apparatus and a method for driving a hydraulic system of a construction machine, in particular a hydraulic excavator.
2. Discussion of the Prior Art
As is generally known, the hydraulic system of a powerful hydraulic excavator has a plurality of control blocks fed via a pump each. Each control block is used to drive a plurality of hydraulic actuators. Thus, for example, a first control block can drive the working equipment as well as the right-hand running gear, a second control block can drive the working equipment as well as the left-hand running gear, a third control block can drive the working equipment as well as the slewing mechanism, and a fourth control block can drive the working equipment as well as, likewise, the slewing mechanism. This division of the pump output between the control blocks ensures the effective supply of the various hydraulic actuators with pressure medium.
Since it is customary for the slewing mechanism to be switched on only for about 25% of a working cycle, here the pump of the slewing mechanism circuit can also be used for the working equipment circuit. When the movement of the slewing mechanism is initiated, however, the quantity delivered by the pump is concentrated onto the slewing mechanism circuit. As a result of this, it is no longer available to the working equipment circuit, in particular the boom cylinder. On the other hand, a major part of the available quantity delivered by the pump is only needed at the end of the acceleration phase of the slewing unit, since at the beginning of the acceleration phase it is a high torque (pump pressure) at a low speed (pump delivery quantity) which is preferentially needed. Only when the angular speed of the slewing mechanism superstructure rises does the requirement on the quantity delivered by the pump rise accordingly, the ultimate consequence of which is that as the angular speed of the superstructure rises, a slowing down of the movement of the working equipment, in particular the boom, occurs.